Need help. i learned this already i jus need a refresher. thanks

Any is very appreciated! (picture is provided below)not sure how to do this at all won't lie

What is the solution to the equation? k/6.4=8.7 2.3 5.568 15.1 55.68

Some boys and girls were asked if they had a pet. one third of the group were boys. there were 20 boys. 20% of the girls had a pet. boys with a pet : girls with a pet = 1 : 5 i need to know how many girls there are.